Which Open Source E-Mail Archiving Software [for 2025]?

Open Source Email Archiving: The Basics

What is email archiving?

Email archiving means storing emails long-term in an unchangeable format after people finish processing them in their inboxes.

And yet, true email archiving requires keeping original digital data uncompressed. Your electronic archives must also pass audits.

Microsoft Exchange handles the initial delivery to the correct mailbox. After that, users decide to either rely on Outlook's built-in archiving or switch to a revision-proof system.

► Contact our team for a free live presentation

Why email archiving?

Almost every employee relies on email daily. But here's the thing: you have to store those processed emails legally and securely.

EU rules have allowed unsigned email invoices since July 2011. This means countless business emails now fall under commercial law, including the German Fiscal Code (AO), GoBD, GoBS, GDPdU, and the GDPR.

A digital email carries the exact same legal weight as a paper document. Beyond compliance, a proper DMS brings huge benefits. You stop making distribution copies, and you rarely lose documents.

What are the retention periods for archiving emails?

Content dictates how long you must keep an email. The exact same rules apply to paper and digital records. The Federal Ministry of Finance requires you to hold the following documents for six years*:

received business letters
Reminders
Accepted offers

You need to keep these business emails for at least ten years*:

Invoices
Tax returns
Inventories
Profit and loss balance sheet
Logbook

* Quelle: Bundesministerium der Finanzen (2020). The list described is not complete and serves only as an example for illustration. It may not apply outside of germany.

The practice of email archiving in companies

How does email archiving work in Microsoft Outlook?

Outlook's native archiving works fine for private use if you don't need legally secure records. The software automatically archives standard folders like your inbox on a rolling six-month schedule.

You can also archive emails manually. You simply create an archive folder, right-click the entry, and send the relevant emails to the archive.

How do you archive emails with a document management system in an audit-proof manner?

Document management systems and enterprise content management systems solve this problem. bitfarm-Archiv connects directly to Microsoft Outlook. You can let users archive manually or set the system to capture entire mailboxes automatically. Watch the video below to see how email archiving and document imports work.

We also built interfaces for systems like Tobit David, Lotus Notes, Thunderbird, and Kerio to ensure GoBS and GDPdU compliance. You can even secure POP3 and IMAP4 accounts using the bitfarm-Archiv POP3 connector. The DMS can then process those emails directly.

Imagine setting up a POP3 account like "invoices@company.com" and giving it to your suppliers. The system instantly routes incoming invoices from that address straight to the right clerk for approval, and then pushes them to accounting.

So, you get the exact same workflow for email invoices that you used to use for paper. The DMS treats a scanned paper invoice and a PDF email attachment exactly the same way. You can even set the system to automatically email your own outgoing invoices.

In 2 steps to audit-proof email archiving with bitfarm-Archiv

Our open-source DMS directly connects to Outlook as a simple add-in. Archiving an email takes just two steps:

1. Choose automatic or manual archiving

2. Archive the document in the client

Users first decide whether to automate the process or handle it manually. Manual archiving gives you extra choices, like picking a specific target archive.

Clicking either button sends the email straight into the document management system. bitfarm-Archiv drops these into the importer by default. From there, you pick the target archive and configure your options.

Hitting "Archive" locks the email away securely. The system immediately marks it in Outlook so you always know exactly what you have already archived.

Best practices for open source email archiving

Sometimes you just need the attachments, not the entire email body. GoBD rules allow you to archive only the attachments when that happens. Skipping the email body stops redundant files from clogging up your DMS. It also speeds up future searches because the system only digs through data that actually matters.

You just click the "Attachments only" button in bitfarm-Archiv to handle this. The system instantly routes every attachment from that email right into your archive.

But here's the thing: you might only want one specific attachment from an email. You can grab it using manual archiving. Just click "Select attachments manually" in the tab. A window pops up beneath the email, letting you pick exactly which file to save.

What other reasons are there for archiving email with a DMS?

Archiving also takes the load off your main email server. You can delete older emails from the server once they hit the archive, keeping your active databases lean. Anyone running MS-Exchange knows how painfully slow a massive Outlook mailbox gets when you try to open it.

Let's be honest, Outlook's native search runs slowly and misses things. A dedicated document management system searches faster, tracks down exact matches, and scans deep inside your email attachments all at once.

What problems arise when it comes to data protection and email archiving?

Archiving every company email creates a huge privacy problem when employees send personal messages. And yet, filtering business traffic from private traffic perfectly is almost impossible.

You basically have two options. Users can archive selectively, or management can ban private emails entirely. Once a ban is in place, you can safely archive everything. If a private email slips through, the employer no longer carries the legal liability.

Trivia around the topic of emails

Ray Tomlinson sent the very first email in 1971 to a second PC sitting right next to him
People send roughly 2.8 million emails worldwide every single second
The average person checks their inbox 15 times a day
Surveys show 86% of entrepreneurs prefer email because it leaves a clear legal paper trail
Spam made up nearly 60% of all global email traffic in 2019

Open Source Email Archiving: The Guide for Audit-Proof Archiving in 2025

The essentials in brief